Method and apparatus for configuring and signalling PTRS in a telecommunication system

ABSTRACT

The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). Disclosed is a method of defining a resource block or resource element offset for mapping PTRS to a symbol, wherein the offset is determined based on an identifier of a particular user equipment, UE.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 of International Application No.PCT/KR2018/012645 filed on Oct. 24, 2018, which claims priority toUnited Kingdom Patent Application No. 1719102.4 filed on Nov. 17, 2017,the disclosures of which are herein incorporated by reference in theirentirety.

BACKGROUND 1. Field

The present disclosure relates to a telecommunication system. Itparticularly relates to a so-called New Radio (NR) or Fifth Generation(5G) telecommunication system making use of the Bandwidth Parts (BWP)functionality.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4th generation (4G) communication systems, efforts havebeen made to develop an improved 5th generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution(LTE) System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 28 GHz or 60 GHz bands, so as toaccomplish higher data rates. To decrease propagation loss of the radiowaves and increase the transmission distance, the beamforming, massivemultiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO),array antenna, an analog beam forming, large scale antenna techniquesare discussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid frequency shift keying (FSK) and quadratureamplitude modulation (FQAM) and sliding window superposition coding(SWSC) as an advanced coding modulation (ACM), and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

The BWP functionality allows available radio spectrum to be subdividedin a manner whereby each part of the BWP assignment can operateaccording to different parameters. For instance, a User Equipment (UE)can be allocated up to 4 BWPs with one being assigned to a particularservice or class of data with specific numerology, for instance.

One particular parameter which can vary across different BWPs is thephase tracking reference signal (PTRS). This is provided to allow the UEto compensate for phase variations in a received resource element (RE).The density/pattern of PTRS may vary due to many factors, for instance15 KHz to 60 KHz sub-carrier spacings in different BWPs.

One problem may be inter-UE interference on PTRS symbols. In order toaddress this problem, RB level PTRS offset is introduced. This RB levelPTRS offsets may also depend on the configurations of BWPs inneighbouring UEs. Considering the fact that other PTRS configurationparameters also depend on the BWP configuration, with multiple BWPsconfigured to a specific UE, the signalling overhead could besignificant and the embodiments of the present disclosure aim to addresssuch problems.

SUMMARY

An objective of embodiments of this invention is to address possibleissues with RRC configuration and UE reporting for PTRS per bandwidthpart (BWP). In other words, there may be excessive signalling requiredand embodiments of the present disclosure seek to reduce such signallingoverhead.

According to the present disclosure there is provided an apparatus andmethod as set forth in the appended claims. Other features of theinvention will be apparent from the dependent claims, and thedescription which follows.

According to a first aspect of the invention, there is provided a methodof defining a Resource Block or Resource Element offset for mapping PTRSto a symbol, wherein the offset is determined based on an identifier ofa particular User Equipment, UE.

According to a second aspect of the invention, there is provided amethod for operating of a base station (BS) in a wireless communicationsystem, the method comprising determining at least one PTRSconfiguration by determining resource block (RB) and/or resource element(RE) offset for mapping phase tracking reference signal (PTRS) to ascheduled RBs, wherein the scheduled RBs are allocated to a particularuser equipment (UE) for data transmission, transmitting the at least onePTRS configuration and mapping PTRS to symbols designated by the offsetin the scheduled RBs, wherein the offset is determined based on anidentifier of a particular User Equipment, UE.

In an embodiment, the identifier for the UE is configured by the networkand the offset is determined by the UE. The network comprises one ormore network entities, such as controllers and base stations.

In an embodiment, the offset is determined according to one of:

$\begin{matrix}{{RB_{offset}} = \left\lfloor \frac{C - {RNTI}}{1\text{/}FD} \right\rfloor} & \left( {1a} \right) \\{{RB}_{offset} = {{1\text{/}FD} - \left\lfloor \frac{C - {RNTI}}{1\text{/}FD} \right\rfloor}} & \left( {1b} \right) \\{{RB}_{offset} = \left\lfloor \frac{{{partial}\mspace{14mu} C} - {RNTI}}{1\text{/}FD} \right\rfloor} & (2) \\{or} & \; \\{{the}\mspace{14mu}{last}\mspace{14mu}{\log_{2}\left( {1\text{/}{FD}} \right)}\mspace{14mu}{bits}\mspace{14mu}{of}\mspace{14mu} C\text{-}{{RNTI}.}} & (3)\end{matrix}$

In an embodiment, the offset is configured on a per-BWP basis.

In an embodiment, a PTRS configuration may be determined on a per-BWPbasis and is transmitted to the UE using an offset configuration whereonly a difference between a default configuration and the determinedconfiguration is transmitted to the UE.

In an embodiment, a PTRS configuration may be determined on a per-BWPbasis and is transmitted to the UE using an additional bit, whereby theadditional bit is used to indicate the use of a default configuration.

In an embodiment, a PTRS configuration may be determined on a per-BWPbasis and is transmitted to the UE using a codeword, whereby an agreedscheme is used to transmit the PTRS configuration.

In an embodiment, more common configurations have shorter codewords.

In an embodiment, the configuration is transmitted either by RRC or DCIsignalling.

In an embodiment, the PTRS configuration comprises one or more of RBoffset, frequency density table thresholds and time density tablethresholds.

In an embodiment, the default configuration is a configuration fordefault BWP.

In an embodiment, the PTRS configuration is recommended by and reportedby the UE.

In an embodiment, the UE reporting is performed by one of UCI or UECapability Signalling.

According to a second aspect, apparatus is arranged to perform themethod of the first aspect.

In an embodiment, the apparatus comprises a network entity and a UserEquipment.

Although a few preferred embodiments of the present disclosure have beenshown and described, it will be appreciated by those skilled in the artthat various changes and modifications might be made without departingfrom the scope of the invention, as defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show how embodimentsof the same may be carried into effect, reference will now be made, byway of example, to the accompanying diagrammatic drawings in which:

FIG. 1 illustrates a wireless communication system according to variousembodiments of the present disclosure;

FIG. 2 illustrates the BS in the wireless communication system accordingto various embodiments of the present disclosure;

FIG. 3 illustrates the terminal in the wireless communication systemaccording to various embodiments of the present disclosure;

FIG. 4 illustrates the communication interface in the wirelesscommunication system according to various embodiments of the presentdisclosure; and

FIG. 5 shows a representation of BWP configuration.

DETAILED DESCRIPTION

Hereinafter, in various embodiments of the present disclosure, hardwareapproaches will be described as an example. However, various embodimentsof the present disclosure include a technology that uses both hardwareand software and thus, the various embodiments of the present disclosuremay not exclude the perspective of software.

Hereinafter, the present disclosure describes technology for identifyingsymbols for PTRS in a wireless communication system.

The terms referring to a signal, the terms referring to a channel, theterms referring to control information, the terms referring to a networkentity, and the terms referring to elements of a device used in thefollowing description are used only for convenience of the description.Accordingly, the present disclosure is not limited to the followingterms, and other terms having the same technical meaning may be used.

Further, although the present disclosure describes various embodimentsbased on the terms used in some communication standards (for example,3rd Generation Partnership Project (3GPP)), they are only examples forthe description. Various embodiments of the present disclosure may beeasily modified and applied to other communication systems.

FIG. 1 illustrates a wireless communication system according to variousembodiments of the present disclosure. In FIG. 1, a base station (BS)110, a terminal 120, and a terminal 130 are illustrated as the part ofnodes using a wireless channel in a wireless communication system. FIG.1 illustrates only one BS, but another BS, which is the same as orsimilar to the BS 110, may be further included.

The BS 110 is network infrastructure that provides wireless access tothe terminals 120 and 130. The BS 110 has coverage defined as apredetermined geographical region based on the distance at which asignal can be transmitted. The BS 110 may be referred to as “accesspoint (AP),” “eNodeB (eNB),” “5th generation (5G) node,” “wirelesspoint,” “transmission/reception Point (TRP)” as well as “base station.”

Each of the terminals 120 and 130 is a device used by a user, andperforms communication with the BS 110 through a wireless channel.Depending on the case, at least one of the terminals 120 and 130 mayoperate without user involvement. That is, at least one of the terminals120 and 130 is a device that performs machine-type communication (MTC)and may not be carried by the user. Each of the terminals 120 and 130may be referred to as “user equipment (UE),” “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” or “userdevice” as well as “terminal.”

The BS 110, the terminal 120, and the terminal 130 may transmit andreceive wireless signals in millimeter wave (mmWave) bands (for example,28 GHz, 30 GHz, 38 GHz, and 60 GHz). At this time, in order to improve achannel gain, the BS 110, the terminal 120, and the terminal 130 mayperform beamforming. The beamforming may include transmissionbeamforming and reception beamforming. That is, the BS 110, the terminal120, and the terminal 130 may assign directivity to a transmissionsignal and a reception signal. To this end, the BS 110 and the terminals120 and 130 may select serving beams 112, 113, 121, and 131 through abeam search procedure or a beam management procedure. After that,communications may be performed using resources having a quasico-located relationship with resources carrying the serving beams 112,113, 121, and 131.

A first antenna port and a second antenna ports are considered to bequasi co-located if the large-scale properties of the channel over whicha symbol on the first antenna port is conveyed can be inferred from thechannel over which a symbol on the second antenna port is conveyed. Thelarge-scale properties may include one or more of delay spread, dopplerspread, doppler shift, average gain, average delay, and spatial Rxparameters.

FIG. 2 illustrates the BS in the wireless communication system accordingto various embodiments of the present disclosure. A structureexemplified at FIG. 2 may be understood as a structure of the BS 110.The term “-module”, “-unit” or “-er” used hereinafter may refer to theunit for processing at least one function or operation and may beimplemented in hardware, software, or a combination of hardware andsoftware.

Referring to FIG. 2, the BS may include a wireless communicationinterface 210, a backhaul communication interface 220, a storage unit230, and a controller 240.

The wireless communication interface 210 performs functions fortransmitting and receiving signals through a wireless channel. Forexample, the wireless communication interface 210 may perform a functionof conversion between a baseband signal and bitstreams according to aphysical layer standard of the system. For example, in datatransmission, the wireless communication interface 210 generates complexsymbols by encoding and modulating transmission bitstreams. Further, indata reception, the wireless communication interface 210 reconstructsreception bitstreams by demodulating and decoding the baseband signal.

In addition, the wireless communication interface 210 up-converts thebaseband signal into an Radio Frequency (RF) band signal, transmits theconverted signal through an antenna, and then down-converts the RF bandsignal received through the antenna into the baseband signal. To thisend, the wireless communication interface 210 may include a transmissionfilter, a reception filter, an amplifier, a mixer, an oscillator, adigital-to-analog convertor (DAC), an analog-to-digital convertor (ADC),and the like. Further, the wireless communication interface 210 mayinclude a plurality of transmission/reception paths. In addition, thewireless communication interface 210 may include at least one antennaarray consisting of a plurality of antenna elements.

On the hardware side, the wireless communication interface 210 mayinclude a digital unit and an analog unit, and the analog unit mayinclude a plurality of sub-units according to operation power, operationfrequency, and the like. The digital unit may be implemented as at leastone processor (e.g., a digital signal processor (DSP)).

The wireless communication interface 210 transmits and receives thesignal as described above. Accordingly, the wireless communicationinterface 210 may be referred to as a “transmitter” a “receiver,” or a“transceiver.” Further, in the following description, transmission andreception performed through the wireless channel may be used to have ameaning including the processing performed by the wireless communicationinterface 210 as described above.

The backhaul communication interface 220 provides an interface forperforming communication with other nodes within the network. That is,the backhaul communication interface 220 converts bitstreams transmittedto another node, for example, another access node, another BS, a highernode, or a core network, from the BS into a physical signal and convertsthe physical signal received from the other node into the bitstreams.

The storage unit 230 stores a basic program, an application, and datasuch as setting information for the operation of the BS 110. The storageunit 230 may include a volatile memory, a non-volatile memory, or acombination of volatile memory and non-volatile memory. Further, thestorage unit 230 provides stored data in response to a request from thecontroller 240.

The controller 240 controls the general operation of the BS. Forexample, the controller 240 transmits and receives a signal through thewireless communication interface 210 or the backhaul communicationinterface 220. Further, the controller 240 records data in the storageunit 230 and reads the recorded data. The controller 240 may performsfunctions of a protocol stack that is required from a communicationstandard. According to another implementation, the protocol stack may beincluded in the wireless communication interface 210. To this end, thecontroller 240 may include at least one processor. According to variousembodiments, the controller 240 may include PTRS mapping function. Here,the PTRS mapping function may be a command/code temporarily resided inthe controller 240, a storage space that stores the command/code, or apart of circuitry of the controller 240.

According to exemplary embodiments of the present disclosure, thecontroller 240 may determine offset of RE for mapping a PTRS andtransmit related information to UEs. For example, the controller 240 maycontrol the base station to perform operations according to theexemplary embodiments of the present disclosure.

FIG. 3 illustrates the terminal in the wireless communication systemaccording to various embodiments of the present disclosure. A structureexemplified at FIG. 3 may be understood as a structure of the terminal120 or the terminal 130. The term “-module”, “-unit” or “-er” usedhereinafter may refer to the unit for processing at least one functionor operation, and may be implemented in hardware, software, or acombination of hardware and software.

Referring to FIG. 3, the terminal 120 includes a communication interface310, a storage unit 320, and a controller 330.

The communication interface 310 performs functions fortransmitting/receiving a signal through a wireless channel. For example,the communication interface 310 performs a function of conversionbetween a baseband signal and bitstreams according to the physical layerstandard of the system. For example, in data transmission, thecommunication interface 310 generates complex symbols by encoding andmodulating transmission bitstreams. Also, in data reception, thecommunication interface 310 reconstructs reception bitstreams bydemodulating and decoding the baseband signal. In addition, thecommunication interface 310 up-converts the baseband signal into an RFband signal, transmits the converted signal through an antenna, and thendown-converts the RF band signal received through the antenna into thebaseband signal. For example, the communication interface 310 mayinclude a transmission filter, a reception filter, an amplifier, amixer, an oscillator, a DAC, and an ADC.

Further, the communication interface 310 may include a plurality oftransmission/reception paths. In addition, the communication interface310 may include at least one antenna array consisting of a plurality ofantenna elements. In the hardware side, the wireless communicationinterface 210 may include a digital circuit and an analog circuit (forexample, a radio frequency integrated circuit (RFIC)). The digitalcircuit and the analog circuit may be implemented as one package. Thedigital circuit may be implemented as at least one processor (e.g., aDSP). The communication interface 310 may include a plurality of RFchains. The communication interface 310 may perform beamforming.

The communication interface 310 transmits and receives the signal asdescribed above. Accordingly, the communication interface 310 may bereferred to as a “transmitter,” a “receiver,” or a “transceiver.”Further, in the following description, transmission and receptionperformed through the wireless channel is used to have a meaningincluding the processing performed by the communication interface 310 asdescribed above.

The storage unit 320 stores a basic program, an application, and datasuch as setting information for the operation of the terminal 120. Thestorage unit 320 may include a volatile memory, a non-volatile memory,or a combination of volatile memory and non-volatile memory. Further,the storage unit 320 provides stored data in response to a request fromthe controller 330.

The controller 330 controls the general operation of the terminal 120.For example, the controller 330 transmits and receives a signal throughthe communication interface 310. Further, the controller 330 recordsdata in the storage unit 320 and reads the recorded data. The controller330 may performs functions of a protocol stack that is required from acommunication standard. According to another implementation, theprotocol stack may be included in the communication interface 310. Tothis end, the controller 330 may include at least one processor ormicroprocessor, or may play the part of the processor. Further, the partof the communication interface 310 or the controller 330 may be referredto as a communication processor (CP). According to various embodiments,the controller 330 may include an identifying function for identifyingthe location of the transmitted PTRS. Here, the identifying function maybe a command/code temporarily resided in the controller 330, a storagespace that stores the command/code, or a part of circuitry of thecontroller 330.

FIG. 4 illustrates the communication interface in the wirelesscommunication system according to various embodiments of the presentdisclosure. FIG. 4 shows an example for the detailed configuration ofthe communication interface 210 of FIG. 2 or the communication interface310 of FIG. 3. More specifically, FIG. 4 shows elements for performingbeamforming as part of the communication interface 210 of FIG. 2 or thecommunication interface 310 of FIG. 3.

Referring to FIG. 4, the communication interface 210 or 310 includes anencoding and circuitry 402, a digital circuitry 404, a plurality oftransmission paths 406-1 to 406-N, and an analog circuitry 408.

The encoding and circuitry 402 performs channel encoding. For thechannel encoding, at least one of a low-density parity check (LDPC)code, a convolution code, and a polar code may be used. The encoding andcircuitry 402 generates modulation symbols by performing constellationmapping.

The digital circuitry 404 performs beamforming for a digital signal (forexample, modulation symbols). To this end, the digital circuitry 404multiples the modulation symbols by beamforming weighted values. Thebeamforming weighted values may be used for changing the size and phraseof the signal, and may be referred to as a “precoding matrix” or a“precoder.” The digital circuitry 404 outputs the digitally beamformedmodulation symbols to the plurality of transmission paths 406-1 to406-N. At this time, according to a multiple input multiple output(MIMO) transmission scheme, the modulation symbols may be multiplexed,or the same modulation symbols may be provided to the plurality oftransmission paths 406-1 to 406-N.

The plurality of transmission paths 406-1 to 406-N convert the digitallybeamformed digital signals into analog signals. To this end, each of theplurality of transmission paths 406-1 to 406-N may include an inversefast Fourier transform (IFFT) calculation unit, a cyclic prefix (CP)insertion unit, a DAC, and an up-conversion unit. The CP insertion unitis for an orthogonal frequency division multiplexing (OFDM) scheme, andmay be omitted when another physical layer scheme (for example, a filterbank multi-carrier: FBMC) is applied. That is, the plurality oftransmission paths 406-1 to 406-N provide independent signal processingprocesses for a plurality of streams generated through the digitalbeamforming. However, depending on the implementation, some of theelements of the plurality of transmission paths 406-1 to 406-N may beused in common.

The analog circuitry 408 performs beamforming for analog signals. Tothis end, the digital circuitry 404 multiples the analog signals bybeamforming weighted values. The beamformed weighted values are used forchanging the size and phrase of the signal. More specifically, accordingto a connection structure between the plurality of transmission paths406-1 to 406-N and antennas, the analog circuitry 408 may be configuredin various ways. For example, each of the plurality of transmissionpaths 406-1 to 406-N may be connected to one antenna array. In anotherexample, the plurality of transmission paths 406-1 to 406-N may beconnected to one antenna array. In still another example, the pluralityof transmission paths 406-1 to 406-N may be adaptively connected to oneantenna array, or may be connected to two or more antenna arrays.

Methods according to embodiments stated in claims and/or specificationsof the present disclosure may be implemented in hardware, software, or acombination of hardware and software.

When the methods are implemented by software, a computer-readablestorage medium for storing one or more programs (software modules) maybe provided. The one or more programs stored in the computer-readablestorage medium may be configured for execution by one or more processorswithin the electronic device. The at least one program may includeinstructions that cause the electronic device to perform the methodsaccording to various embodiments of the present disclosure as defined bythe appended claims and/or disclosed herein.

The programs (software modules or software) may be stored innon-volatile memories including a random access memory and a flashmemory, a read only memory (ROM), an electrically erasable programmableread only memory (EEPROM), a magnetic disc storage device, a compactdisc-ROM (CD-ROM), digital versatile discs (DVDs), or other type opticalstorage devices, or a magnetic cassette. Alternatively, any combinationof some or all of the may form a memory in which the program is stored.Further, a plurality of such memories may be included in the electronicdevice.

In addition, the programs may be stored in an attachable storage devicewhich is accessible through communication networks such as the Internet,Intranet, local area network (LAN), wide area network (WAN), and storagearea network (SAN), or a combination thereof. Such a storage device mayaccess the electronic device via an external port. Further, a separatestorage device on the communication network may access a portableelectronic device.

In the above-described detailed embodiments of the present disclosure, acomponent included in the present disclosure is expressed in thesingular or the plural according to a presented detailed embodiment.However, the singular form or plural form is selected for convenience ofdescription suitable for the presented situation, and variousembodiments of the present disclosure are not limited to a singleelement or multiple elements thereof. Further, either multiple elementsexpressed in the description may be configured into a single element ora single element in the description may be configured into multipleelements.

While the present disclosure has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the scope of the present disclosure. Therefore,the scope of the present disclosure should not be defined as beinglimited to the embodiments, but should be defined by the appended claimsand equivalents thereof.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

The BWP functionality allows available radio spectrum to be subdividedin a manner whereby each part of the BWP assignment can operateaccording to different parameters. For instance, a User Equipment (UE)can be allocated up to 4 BWPs with one being assigned to a particularservice or class of data with specific numerology, for instance.

FIG. 5 shows how BWPs may be configured in the frequency/time space. Aparticular UE or terminal is configured with 4 BWPs. BWP1 hasconfiguration A; BWP2 has configuration B; BWP3 and BWP4 have identicalconfigurations C. This figure illustrates that different operationalparameters may apply in different BWPs and the UE can switch betweenthem as required.

According to exemplary embodiments of the present disclosure, thecontroller 330 may receive parameters related to the location of thePTRS by higher layer signalling or DCI. For example, the controller 330may control the terminal to perform operations according to theexemplary embodiments of the present disclosure.

One particular parameter which can vary across different BWPs is thephase tracking reference signal (PTRS). This is provided to allow the UEto compensate for phase variations in a received resource element (RE).The density/pattern of PTRS may vary due to many factors, for instance15 KHz to 60 KHz sub-carrier spacings in different BWPs.

It has been agreed as part of the standardization procedure that, foreach serving cell,

-   -   the maximum number of DL/UL BWP configurations is:        -   For paired spectrum: 4 DL BWPs and 4 UL BWPs        -   For unpaired spectrum: 4 DL/UL BWP pairs        -   For SUL: 4 UL BWPs    -   RRC configuration of thresholds in density tables:    -   UE is configured with two sets of thresholds        M={ptrsthMCS_(j),j=1, 2, 3, 4} and R={ptrsthRB_(n),n=0, 2, 4},        independently per BWP, using dedicated RRC signaling for UL and        DL respectively    -   UE capability signaling of thresholds    -   A UE capability signals a recommended {M,R} for UL and DL        respectively    -   The recommended {M, R} are expected to be larger than the        predefined values    -   Support a Resource Block (RB)-level offset for selecting RBs        among the scheduled RBs for mapping PTRS, and the offset is        implicitly determined by UE-ID (i.e., C-RNTI), wherein the        scheduled RBs are allocated for data transmission to a        particular user equipment (UE).    -   Support implicit derivation the RE-level offset for selecting        subcarrier for mapping PTRS within a RB from one or more        parameters (e.g. associated DMRS port index, SCID, Cell ID, to        be decided in RAN1#91)        -   This can be used at least for avoiding collision with DC            tone    -   In addition, an RRC parameter “PTRS-RE-offset” is also supported        that explicitly indicates the RE-level offset and replaces the        implicit offset, at least for avoiding collision with DC tone

One problem may be inter-UE interference on PTRS symbols. In order toaddress this problem, RB level PTRS offset is introduced. This RB levelPTRS offsets may also depend on the configurations of BWPs inneighbouring UEs. Considering the fact that other PTRS configurationparameters also depend on the BWP configuration, with multiple BWPsconfigured to a specific UE, the signalling overhead could besignificant and the embodiments of the present disclosure aim to addresssuch problems.

It has been agreed as part of the standardization process that anRB-level offset can be applied for selecting RBs among the scheduled RBsfor mapping PTRS, and the offset is implicitly determined by a UEidentifier (UE-ID) i.e., C-RNTI, wherein the scheduled RBs are allocatedfor data transmission to a particular user equipment (UE). However, therules to map C-RNTI to a specific RB offset value are not specified aspart of the standardization process.

This UE-specific offset might also be introduced at the RE, rather thanRB, level. When configuring different RB/RE offsets for different UEs,the following multiple-to-one mapping problem might occur.

Essentially, RB/RE offset has limited options, e.g. for RB offset withFrequency Density (FD)=½, the RB offset can only be 0 or 1. However, UEspecific configuration parameters, such as, C-RNTI, have many moreoptions available. One possible mapping rule from C-RNTI to RB offsetcan thus be defined as:

${RB_{offset}} = \left\lfloor \frac{C - {RNTI}}{1\text{/}FD} \right\rfloor$

In an ideal case with FD=½, half of the UEs associated with one TRP needto have offset=0 and the other half will have offset=1. However, thiscannot be guaranteed without imposing constraints on scheduling, whichis not desirable in NR. Without such constraints, the consequencesinclude multiple UE C-RNTI mapping to one RB offset and, therefore,there is no guarantee that two UEs within one MU-MIMO group havedifferent RB offset and thus no guarantee of interference randomization.

The following alternative solutions can be used to decide offset values:

$\begin{matrix}{{RB_{offset}} = {\left\lfloor \frac{C - {RNTI}}{1\text{/}FD} \right\rfloor\mspace{14mu}{or}}} & \left( {1a} \right) \\{{RB}_{offset} = {{1\text{/}FD} - \left\lfloor \frac{C - {RNTI}}{1\text{/}FD} \right\rfloor}} & \left( {1b} \right) \\{{RB}_{offset} = \left\lfloor \frac{{{partial}\mspace{14mu} C} - {RNTI}}{1\text{/}FD} \right\rfloor} & (2) \\{{Use}\mspace{14mu}{only}\mspace{14mu}{the}\mspace{14mu}{last}\mspace{14mu}{\log_{2}\left( {1\text{/}{FD}} \right)}\mspace{14mu}{bits}\mspace{14mu}{of}\mspace{14mu} C\text{-}{RNTI}} & (3)\end{matrix}$

The first options (1a) and (ab) use the entire C-RNTI string and areleast likely to assign the same offset to different UEs but these havethe highest calculation complexity.

The second option (2) uses only partial C-RNTI (the exact part can bespecified as required), e.g., M bits (M<N)) and thus more likely thanoption (1) to assign the same offset to different UEs and has a lowercalculation complexity than option (1).

The third option (3) is most likely to assign the same offset todifferent UEs but has the lowest calculation complexity of the threeoptions.

The embodiments described above make use of C-RNTI, but note that othertypes of identifier (RNTI), such as RA-RNTI may be used.

Note that the same options can be used for RE level offset if it dependson UE ID or UE specific parameters.

In order to address the one-to-many mapping problem referred to above,RB/RE offset may only be decided by UE specific configuration parameterswhere the mapping is one-to-one to avoid any possible confusion. If thisis not possible in some scenarios, RB/RE offset determined by multipleUE specific configuration parameters may be supported so that based onmultiple rules, only one RB offset value is applied for each individualUE.

It should be noted that when different RB offsets are decided bymultiple rules or parameters, it is desirable to setup a priority levelso that the RB offset value from the rule/parameter with highestpriority is adopted. This priority level can either be implicitlydefined or explicitly signalled to the UE, as required.

The above mentioned configuration of RB/RE offset may be per BWP, i.e.,different BWPs may have different configurations.

It has been agreed in the standardization process that the followingPTRS parameters need to be configured via RRC signaling:

-   -   Frequency Density for CP-OFDM in both DL and UL    -   Time Density for CP_OFDM in both DL and UL    -   Time Density and PTRS chunk size for DTF-s-OFDM

Each one of these parameters may be a structure formed from multipleparameters that control the presence and density of PTRS as a functionof scheduled BW and/or Modulation and Coding Scheme (MCS). Moreover,these parameters need to be configured for each BWP.

Different BWP may have different subcarrier spacing and the aboveparameters may be relevant to subcarrier spacing, although it is notnecessarily advisable to completely re-configure them differently insuch a case. The simplest way is to configure each BWP separately, usinga brute-force technique of explicit configuration. However, consideringthat up to 4 BWPs can be configured, the RRC payload for configuringthese parameters may be quadrupled if 4 BWPs are configured. The payloadcould thus be significant even for RRC configuration.

Based on the fact that the PTRS configuration is not always differentfor different BWP, it is possible to make use of some form of offset RRCconfiguration for multiple BWPs, where PTRS is configured for thedefault BWP via RRC but for the rest of the BWPs, only the differencebetween one BWP and the default BWP is configured via RRC. This has theeffect of reducing RRC payload for PTRS configuration.

Three different embodiments are presented:

(1) Offset Configuration

For the default BWP, an N bits binary sequence a is used to configurePTRS parameters. For a non-default BWP, a further N bits binary sequenceb is used. The difference, i.e., a-b or b-a, is likely to be shorterthan either a or b due to its smaller range. Therefore, for anynon-default BWP, instead of using b, the value of the difference (i.e.,a-b or b-a) can be used to configure PTRS via RRC. This offsetconfiguration may reduce the RRC signaling overhead.

(2) One Additional Indication Bit

In this embodiment, one additional indication bit is configured for eachnon-default BWP. The current agreement is that up to 4 BWPs can beconfigured and if it is assumed that N bits are required to configureall PTRS parameters for each BWP, then 4*N bits are required in total.

However, with one additional indication bit, N bits may still be used toconfigure the default BWP but for other non-default BWPs, if the BWPconfiguration is the same as the default BWP, the indication bit may beset (or reset) as specified. Therefore, there is no need to useadditional N bits to configure the non-default BWP if its configurationis the same as the default BWP.

In the best case, where all BWP configuration are the same, then for 4BWPs, N+3 bits are required instead of 4*N bits to configure all BWPsvia RRC. In this way, 3*N−3 bits can be saved and RRC signaling overheadis reduced.

In the worst case, where each BWP has a different configuration, 3additional indication bits are required in addition to 4*N bits for PTRSconfiguration. However, the worst case is not likely to occur very oftenso that, in most cases, RRC payload can be significantly reduced.

Note that if it is desired or necessary to retain identicalconfigurations for each payload, it may be necessary to also include theadditional bit, even for the default configuration so that all possibleconfigurations have the same number of bits for each BWP.

(3) Codeword Based Approach

Another possible option for RRC signaling for BWP based PTRSconfiguration is to use codewords for each of the availableconfiguration options. Depending on the probability of the usage of eachPTRS configuration, either variable length code words or a code bookwith fixed length codewords may be used.

If the default PTRS configuration and a few variations are highlyprobable, shorter code words can be used to indicate theseconfigurations, while longer codewords can be used for others. A lengthindicator will be also needed in the message, to effectively decode thecodewords. If there is a more even distribution of configurationoptions, equal length codewords making up a codebook can be used. Inthis case only the index of the codeword (known a-priori by the UE)needs to be transmitted in RRC signaling.

Another issue is that PTRS configuration might not be always necessary,since the default configuration may be used if no significantperformance loss is observed. When RRC configuration is needed, theoffset configuration approach (1) mentioned above can potentially beapplied as well to reduce RRC signaling.

Another use case is when RRC reconfiguration needs to be carried out forPTRS configuration, the offset configuration approach can be employed.

The benefit of configuring PTRS for all BWPs via RRC is when BWPswitching happens, there is no need to configure PTRS again and thuslatency due to BWP switching can be reduced. At any one time, only oneBWP can be activated for the UE. The UE starts on the default BWP andwill switch to another BWP if instructed or if deemed necessary. Oncethe switch occurs, a timer is started and the UE switched back to thedefault BWP upon expiry of the timer.

However, the disadvantage of RRC configuration is that it issemi-persistent, meaning that the configuration cannot be changeddynamically. In this regard, Downlink Control Indicator (DCI)configuration can also be used to configure PTRS parameters when BWPswitching happens. The above mentioned three options can be employed forDCI configuration as well. DCI configuration can occur every slot, sothat the configuration can be changed every slot in a dynamic manner.However, RRC configuration only occurs at the beginning of atransmission and so will persist for several slots/sub-frames/frames. Itis therefore considered semi-persistent.

It has been agreed in the standardization procedure that the UE mayrecommend two sets of thresholds for frequency and time density tables,respectively, and the UE report should also be provided per BWP.Following the same rationale as above, the payload of UE reporting maybe significant if multiple BWPs are configured. In this regard, thethree options mentioned above for RRC configuration may also be appliedfor a UE report to reduce the UE report signaling overhead. The UEreporting can be done via UCI or UE Capability signaling.

One additional use case is that when the UE decides to report a new setof thresholds different from the previous set for some reason, offsetreporting can be used to reduce signaling overhead.

For a better understanding of the invention, and to show how embodimentsof the same may be carried into effect, reference will now be made, byway of example only, to the accompanying diagrammatic drawings in which:

At least some of the example embodiments described herein may beconstructed, partially or wholly, using dedicated special-purposehardware. Terms such as ‘component’, ‘module’ or ‘unit’ used herein mayinclude, but are not limited to, a hardware device, such as circuitry inthe form of discrete or integrated components, a Field Programmable GateArray (FPGA) or Application Specific Integrated Circuit (ASIC), whichperforms certain tasks or provides the associated functionality. In someembodiments, the described elements may be configured to reside on atangible, persistent, addressable storage medium and may be configuredto execute on one or more processors. These functional elements may insome embodiments include, by way of example, components, such assoftware components, object-oriented software components, classcomponents and task components, processes, functions, attributes,procedures, subroutines, segments of program code, drivers, firmware,microcode, circuitry, data, databases, data structures, tables, arrays,and variables. Although the example embodiments have been described withreference to the components, modules and units discussed herein, suchfunctional elements may be combined into fewer elements or separatedinto additional elements. Various combinations of optional features havebeen described herein, and it will be appreciated that describedfeatures may be combined in any suitable combination. In particular, thefeatures of any one example embodiment may be combined with features ofany other embodiment, as appropriate, except where such combinations aremutually exclusive. Throughout this specification, the term “comprising”or “comprises” means including the component(s) specified but not to theexclusion of the presence of others.

Attention is directed to all papers and documents which are filedconcurrently with or previous to this specification in connection withthis application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

The invention claimed is:
 1. A method performed by a base station (BS)in a wireless communication system, the method comprising: receiving,from a user equipment (UE), UE capability information including: a firstset of thresholds including frequency density thresholds and timedensity thresholds, wherein the first set of thresholds is associatedwith a first subcarrier spacing of subcarrier spacings, and a second setof thresholds including frequency density thresholds and time densitythresholds, wherein the second set of thresholds is associated with asecond subcarrier spacing different from the first subcarrier spacing ofthe subcarrier spacings; identifying a resource block (RB) offsetassociated with a bandwidth part (BWP) based on a frequency density andan identifier of the UE; and mapping at least one phase trackingreference signal (PTRS) based on the RB offset, wherein the BWPcorresponds to one of the subcarrier spacings.
 2. The method of claim 1,wherein each of the first set of thresholds and the second set ofthresholds is associated with one of a downlink (DL) PTRS and an uplink(UL) PTRS.
 3. The method of claim 1, wherein the RB offset is identifiedbased on a modulo operation of the identifier of the UE and thefrequency density.
 4. The method of claim 1, further comprising:transmitting, to the UE via a radio resource control (RRC) signaling, aPTRS configuration for the BWP including information on a resourceelement (RE) offset, information related to the frequency density, andinformation related to a time density, wherein the at least one PTRS ismapped to a resource based on the RB offset and the RE offset.
 5. Themethod of claim 1, wherein the RB offset is configured per a BWP.
 6. Amethod performed by a user equipment (UE) in a wireless communicationsystem, the method comprising: transmitting, to a base station (BS), UEcapability information including: a first set of thresholds includingfrequency density thresholds and time density thresholds, wherein thefirst set of thresholds is associated with a first subcarrier spacing ofsubcarrier spacings, and a second set of thresholds including frequencydensity thresholds and time density thresholds, the second set ofthresholds being associated with a second subcarrier spacing differentfrom the first subcarrier spacing of the subcarrier spacings, wherein: abandwidth part (BWP) corresponds to one of the subcarrier spacings, aresource block (RB) offset associated with the BWP is identified basedon a frequency density and an identifier of the UE, and the RB offset isused to map at least one phase tracking reference signal (PTRS).
 7. Themethod of claim 6, wherein each of the first set of thresholds and thesecond set of thresholds is associated with one of a downlink (DL) PTRSand an uplink (UL) PTRS.
 8. The method of claim 6, wherein the RB offsetis identified based on a modulo operation of the identifier of the UEand the frequency density.
 9. The method of claim 6, further comprising:receiving, from the BS via a radio resource control (RRC) signaling, aPTRS configuration for the BWP including information on a resourceelement (RE) offset, information related to the frequency density andinformation related to a time density, wherein the at least one PTRS ismapped to a resource based on the RB offset and the RE offset.
 10. Themethod of claim 6, wherein the RB offset is configured per a BWP.
 11. Abase station (BS) in a wireless communication system, the BS comprising:a transceiver; and at least one processor coupled to the transceiver,the at least one processor configured to: receive, from a user equipment(UE), UE capability information including: a first set of thresholdsincluding frequency density thresholds and time density thresholds,wherein the first set of thresholds is associated with a firstsubcarrier spacing of subcarrier spacings, and a second set ofthresholds including frequency density thresholds and time densitythresholds, wherein the second set of thresholds is associated with asecond subcarrier spacing different from the first subcarrier spacing ofthe subcarrier spacings, identify a resource block (RB) offsetassociated with a bandwidth part (BWP) based on a frequency density andan identifier of the UE, and map at least one phase tracking referencesignal (PTRS) based on the RB offset, wherein the BWP corresponds to oneof the subcarrier spacings.
 12. The BS of claim 11, wherein each of thefirst set of thresholds and the second set of thresholds is associatedwith one of a downlink (DL) PTRS and an uplink (UL) PTRS.
 13. The BS ofclaim 11, wherein the RB offset is identified based on a modulooperation of the identifier of the UE and the frequency density.
 14. TheBS of claim 11, wherein: the at least one processor is furtherconfigured to transmit, to the UE via a radio resource control (RRC)signaling, a PTRS configuration for the BWP including information on aresource element (RE) offset, information related to the frequencydensity and information related to a time density; and the at least onePTRS is mapped to a resource based on the RB offset and the RE offset.15. The BS of claim 11, wherein the RB offset is configured per a BWP.16. A user equipment (UE) in a wireless communication system, the UEcomprising: a transceiver; and at least one processor coupled to thetransceiver, the at least one processor configured to: transmit, to abase station (BS), UE capability information including: a first set ofthresholds including frequency density thresholds and time densitythresholds, wherein the first set of thresholds is associated with afirst subcarrier spacing of subcarrier spacings, and a second set ofthresholds including frequency density thresholds and time densitythresholds, the second set of thresholds being associated with a secondsubcarrier spacing different from the first subcarrier spacing of thesubcarrier spacings, wherein: a bandwidth part (BWP) corresponds to oneof the subcarrier spacings, a resource block (RB) offset associated withthe BWP is identified based on a frequency density and an identifier ofthe UE, and the RB offset is used to map at least one phase trackingreference signal (PTRS).
 17. The UE of claim 16, wherein each of thefirst set of thresholds and the second set of thresholds is associatedwith one of a downlink (DL) PTRS and an uplink (UL) PTRS.
 18. The UE ofclaim 16, wherein the RB offset is identified based on a modulooperation of the identifier of the UE and the frequency density.
 19. TheUE of claim 16, wherein: the at least one processor is furtherconfigured to receive, from the BS via a radio resource control (RRC)signaling, a PTRS configuration for the BWP including information on aresource element (RE) offset, information related to the frequencydensity and information related to a time density; and the at least onePTRS is mapped to a resource based on the RB offset and the RE offset.20. The UE of claim 16, wherein the RB offset is configured per a BWP.